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[libc] add PREFER_GENERIC flag #73744

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Merged
merged 1 commit into from
Nov 29, 2023
Merged

[libc] add PREFER_GENERIC flag #73744

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10 changes: 3 additions & 7 deletions libc/cmake/modules/LLVMLibCFlagRules.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -132,8 +132,9 @@ endfunction(get_fq_dep_list_without_flag)
# Special flags
set(FMA_OPT_FLAG "FMA_OPT")
set(ROUND_OPT_FLAG "ROUND_OPT")
# SSE2 is the baseline for x86_64, so we add a negative flag to disable it if needed.
set(DISABLE_SSE2_OPT_FLAG "DISABLE_SSE2_OPT")
# This flag will define macros that gated away vectorization code such that
# one can always test the fallback generic code path.
set(PREFER_GENERIC_FLAG "PREFER_GENERIC")

# Skip FMA_OPT flag for targets that don't support fma.
if(NOT((LIBC_TARGET_ARCHITECTURE_IS_X86 AND (LIBC_CPU_FEATURES MATCHES "FMA")) OR
Expand All @@ -145,8 +146,3 @@ endif()
if(NOT(LIBC_TARGET_ARCHITECTURE_IS_X86 AND (LIBC_CPU_FEATURES MATCHES "SSE4_2")))
set(SKIP_FLAG_EXPANSION_ROUND_OPT TRUE)
endif()

# Skip DISABLE_SSE2_OPT flag for targets that don't support SSE2.
if(NOT(LIBC_TARGET_ARCHITECTURE_IS_X86 AND (LIBC_CPU_FEATURES MATCHES "SSE2")))
set(SKIP_FLAG_EXPANSION_DISABLE_SSE2_OPT TRUE)
endif()
18 changes: 9 additions & 9 deletions libc/cmake/modules/LLVMLibCObjectRules.cmake
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Expand Up @@ -18,12 +18,12 @@ function(_get_common_compile_options output_var flags)
set(ADD_SSE4_2_FLAG TRUE)
endif()

list(FIND flags ${DISABLE_SSE2_OPT_FLAG} no_sse2)
if(${no_sse2} LESS 0)
list(FIND flags "${DISABLE_SSE2_OPT_FLAG}__ONLY" no_sse2)
list(FIND flags ${PREFER_GENERIC_FLAG} prefer_generic)
if(${prefer_generic} LESS 0)
list(FIND flags "${PREFER_GENERIC_FLAG}__ONLY" prefer_generic)
endif()
if((${no_sse2} GREATER -1) AND (LIBC_CPU_FEATURES MATCHES "SSE2"))
set(DISABLE_SSE2_FLAG TRUE)
if(${prefer_generic} GREATER -1)
set(ADD_PREFER_GENERIC_FLAG TRUE)
endif()

set(compile_options ${LIBC_COMPILE_OPTIONS_DEFAULT} ${ARGN})
Expand Down Expand Up @@ -66,17 +66,17 @@ function(_get_common_compile_options output_var flags)
if(ADD_SSE4_2_FLAG)
list(APPEND compile_options "-msse4.2")
endif()
if(DISABLE_SSE2_FLAG)
list(APPEND compile_options "-mno-sse2")
if(ADD_PREFER_GENERIC_FLAG)
list(APPEND compile_options "-D__LIBC_PREFER_GENERIC")
endif()
elseif(MSVC)
list(APPEND compile_options "/EHs-c-")
list(APPEND compile_options "/GR-")
if(ADD_FMA_FLAG)
list(APPEND compile_options "/arch:AVX2")
endif()
if(DISABLE_SSE2_FLAG)
list(APPEND compile_options "/arch:SSE")
if(ADD_PREFER_GENERIC_FLAG)
list(APPEND compile_options "/D__LIBC_PREFER_GENERIC")
endif()
endif()
if (LIBC_TARGET_ARCHITECTURE_IS_GPU)
Expand Down
4 changes: 1 addition & 3 deletions libc/src/__support/HashTable/CMakeLists.txt
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@@ -1,11 +1,9 @@
# TODO: `DISABLE_SSE2_OPT` does not quite work yet.
# We will investigate a better way of feature flag control.
add_header_library(
bitmask
HDRS
bitmask.h
FLAGS
DISABLE_SSE2_OPT
PREFER_GENERIC
DEPENDS
libc.src.__support.bit
libc.src.__support.macros.properties.cpu_features
Expand Down
2 changes: 1 addition & 1 deletion libc/src/__support/HashTable/bitmask.h
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Expand Up @@ -85,7 +85,7 @@ template <class BitMask> struct IteratableBitMaskAdaptor : public BitMask {
} // namespace internal
} // namespace LIBC_NAMESPACE

#if defined(LIBC_TARGET_CPU_HAS_SSE2)
#if defined(LIBC_TARGET_CPU_HAS_SSE2) && !defined(__LIBC_PREFER_GENERIC)
#include "sse2/bitmask_impl.inc"
#else
#include "generic/bitmask_impl.inc"
Expand Down